Identifying changes in the reproduction number, rate of spread, and doubling time during the course of the COVID-19 outbreak whilst accounting for potential biases due to delays in case reporting both nationally and subnationally in the United States of America. These results are impacted by changes in testing effort, increases and decreases in testing effort will increase and decrease reproduction number estimates respectively (see Methods or our paper for further explanation).
Using data available up to the: 2020-08-03
Note that it takes time for infection to cause symptoms, to get tested for SARS-CoV-2 infection, for a positive test to return and ultimately to enter the case data presented here. In other words, today’s case data are only informative of new infections about two weeks ago. This is reflected in the plots below, which are by date of infection.
These estimates are available for download here.
Figure 1: The results of the latest reproduction number estimates (based on estimated confirmed cases with a date of infection on the 2020-08-03) in the United States of America, stratified by state, can be summarised by whether confirmed cases are likely increasing or decreasing. This represents the strength of the evidence that the reproduction number in each region is greater than or less than 1, respectively (see the methods for details).
| Estimate | |
|---|---|
| New confirmed cases by infection date | 71263 (27639 – 114351) |
| Expected change in daily cases | Unsure |
| Effective reproduction no. | 0.93 (0.68 – 1.17) |
| Rate of growth | -0.02 (-0.09 – 0.04) |
| Doubling/halving time (days) | -37.7 (15.5 – -7.5) |
Figure 2: A.) Confirmed cases by date of report (bars) and their estimated date of report. B.) Confirmed cases by date of report (bars) and their estimated date of infection. C.) Time-varying estimate of the effective reproduction number. Light ribbon = 90% credible interval; dark ribbon = the 50% credible interval. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.
Figure 3: Confirmed cases with date of infection on the 2020-08-03 and the time-varying estimate of the effective reproduction number (light bar = 90% credible interval; dark bar = the 50% credible interval.). Regions are ordered by the number of expected daily confirmed cases and shaded based on the expected change in daily confirmedcases. The horizontal dotted line indicates the target value of 1 for the effective reproduction no. required for control and a single case required for elimination.
Figure 4: Time-varying estimate of the effective reproduction number (light ribbon = 90% credible interval; dark ribbon = the 50% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.
Figure 5: Confirmed cases by date of report (bars) and their estimated date of infection (light ribbon = 90% credible interval; dark ribbon = the 50% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.
Figure 6: Confirmed cases by date of report (bars) and their estimated date of report (light ribbon = 90% credible interval; dark ribbon = the 50% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.
Figure 7: Time-varying estimate of the effective reproduction number (light ribbon = 90% credible interval; dark ribbon = the 50% credible interval) in all regions. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The horizontal dotted line indicates the target value of 1 for the effective reproduction no. required for control. The vertical dashed line indicates the date of report generation.
Figure 8: Confirmed cases by date of report (bars) and their estimated date of infection (light ribbon = 90% credible interval; dark ribbon = the 50% credible interval) in all regions. Estimates from existing data are shown up to the 2020-08-03 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.